Ratchet blocks typically consist of a sheave rotatably mounted on a shaft between two side plates and a ratchet assembly inside the sheave to allow rotation in one direction only when engaged, and in both directions when disengaged. Typically a ratchet arm is engaged with teeth on the inside of the sheave (or disengaged) by a mechanical switch, which can be thrown only when there is little or no pressure/load on the sheave. Thus if the user wants to shift the block from a ratcheting mode to a freewheeling mode (rotate in either direction) for reduced friction, or from the freewheeling to ratcheting mode to increase, he must physically move to reach the switch with a hand, and concurrently remove the load from any line or wire that is running through the block. In many instances it is not possible to do either, so there is significant friction when the line or wire is eased out through the block as the sheave will not rotate in the direction of easing, or the benefit of ratcheting cannot be attained.
In sailboat racing, where the use of conventional ratchet blocks is widespread, the high friction caused by a ratchet-engaged non-rotating sheave helps reduce the effort required to pull a line through a block under load. However, this friction: 1) reduces the speed by which sailors can execute sail changes such as taking down the spinnaker; 2) encumbers rapid easing of a line attached to a sail; and 3) slows down sail adjustment required for rapid alteration of course and tacking/jibing. The advantage of friction caused by engaging the ratchet when trimming sails is a disadvantage when easing them.
Further, because conventional ratchet blocks require manual switching to change from the ratchet-engaged to freewheeling mode and vice versa, they can only be located where they can be easily reached. On sailboats, this precludes their use high on the mast for halyards, or in other areas where the crew can't normally reach while sailing. It is therefore an objective of the present invention to automatically provide load dependent ratchet action for increased friction and freewheeling for significantly reduced friction, without the manual switching of conventional ratchet blocks. It is also an objective to expand the number of locations for using a ratchet block beyond those normally within easy reach. Further, it is an object of the present invention to provide such a device which is easy and inexpensive to manufacture.